consumption of solar water heater
How much money do you spend on energy consumption in a month? Have you ever thought about a solar water heater as an alternative option?
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If you want to compare which type of heating system is more reasonable for you, stay with us then.
Solar water heating systems are more expensive to buy and install than traditional water heating systems. A solar water heater, on the other hand, may typically save you money in the long term.
The amount of money you save is determined by the following factors:
- The quantity of hot water you use
- The efficiency of your system
- Your geographical location as well as your solar resource
Financing and incentives are available.
The cost of conventional fuels that would otherwise be used by your traditional water heater (natural gas, oil, or electricity)
Installing a solar water heater should reduce your water heating expenditures by 50%-80% on average. Furthermore, because the sun is free, you are immune to future fuel shortages and price increases.
The economics are much more appealing if you are building a new house or refinancing. In most cases, the cost of a solar water heater in new 30-year mortgage costs between $13 and $20 per month.
The federal income tax deduction for solar-related mortgage interest decreases this by around $3-$5 each month. So, if your monthly gasoline savings exceed $15, the solar investment pays for itself very immediately. Every month, you save more than you pay.
Calculating the Energy Efficiency of a Solar Water Heater
To calculate the energy efficiency of a solar water heater, use the solar energy factor (SEF) and a solar fraction (SF). The solar energy factor is defined as the system's energy delivered divided by the system's electrical or gas energy input. The greater the number, the greater the energy efficiency. Solar energy factors range from 1.0 and 11. The most prevalent systems have solar energy factors of 2 or 3.
The sunlight percentage is another performance parameter for solar water heaters. The solar fraction is the proportion of the total conventional hot water heating load that is supplied by solar energy (delivered energy and tank standby losses).
The bigger the solar percentage, the greater the solar contribution to water heating, reducing the amount of energy required by the backup water heater. The solar fraction ranges between 0 and 1.0. Solar fraction levels of 0.5-0.75 are typical.
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The Solar Rating and Certification Corporation list the Solar Energy Factor and Solar Fraction for certified solar hot water systems at https://solar-rating.org/.
This certification also specifies how much heat (kWh or Btu) the system will produce per day under various lighting and temperature circumstances.
Do not select a solar water heating system only based on its energy efficiency. When choosing a solar water heater, you should also consider the size and total cost.
Annual Operating Cost Calculation
Estimate the annual running expenses and compare multiple systems before choosing a solar water heating system. This can help you calculate the energy savings and payback period of investing in a more energy-efficient system, which will almost certainly cost more.
Before you can pick and compare the costs of different systems, you must first determine the system size necessary for your house.
To calculate the annual running cost of a solar water heating system, you will need the following information:
The solar energy component of the system (SEF)
The fuel type and cost of the auxiliary tank (gas or electric) (your local utility can provide current rates).
Then perform the following computations:
First, calculate the amount of energy required to heat the water based on the amount of fuel used or the number of gallons of hot water required.
INCLUDING A GAS AUXILIARY TANK SYSTEM: WATER HEATING ENERGY DAILY
Natural gas, for example, is sometimes sold in "terms." 100,000 British thermal units are equivalent to one (1) therm (Btus). Examine your utility bills to discover how much fuel you use throughout the summer when gas is not utilized for space heating. If you use gas for cooking and drying clothing, you should deduct roughly 60% of your summer total for the energy required to heat water.
The Uniform Energy Factor (UEF) of a typical water heater is the quantity of hot water generated per unit of fuel burned in a standard test.
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The greater the UEF value, the more energy efficient the water heater is. The Department of Energy's test technique is defined in 10 CFR Part 430, Subpart B, Appendix E. A UEF of at least 0.64 is required for residential gas water heaters. Because all of the power flows into the water, the UEF for electric heaters is assumed to be 1.0.
(Summer months fuel use)*EF*0.6/ = Daily Water Heating Energy (number of days in summer months)
The amount of fuel consumed is proportional to the amount of water utilized and the temperature. The energy required to elevate one pound (lbs) of water by one degree Fahrenheit is defined as Btu (F).
- (gallons of hot water per day)*(8.35 lbs/gallon)*(1 BTU/lbs/F)*
- (Temperature difference between hot and cold water)
The DOE test process for water heaters assumes an incoming water temperature of 58°F, a hot water temperature of 135°F, and total hot water production of 64.3 gallons per day, which is the average demand for a three-person family. This equates to 0.4105 therms/day for natural gas and 12.03 kWh per day for electricity.
It is sometimes preferable to scale a solar system based on such benchmark loads or the number of bedrooms in a house rather than actual consumption, which is affected by the changing number and behavior of residents of a residence.
ANNUAL COST OF NATURAL GAS HEATING IN CONVENTION
The annual fuel cost for conventional heating is determined by the Daily Water Heating Energy, the efficiency of the conventional heater, and the fuel price.
Annual Water Heating Cost = (365 days/year) * (Daily Water Heating Energy therms/day) 41,045 UEFSEF Fuel Cost ($/thermBtu) = projected annual operating cost
OR (365 days/year) (0.4105 therms/day) (0.64 USEF) ($1.10/therm) Annual Fuel Cost (therm) = $257.52. yearly operating cost estimate
Example: Assume the SEF is 1.1 and the cost of gas is $1.10/therm 365 0.4105 1.1 $1.10 = $149.83
The energy use per day in the following calculations is based on the DOE water heater test protocol, which assumes an incoming water temperature of 58°F, a hot water temperature of 135°F, and total hot water production of 64.3 gallons per day, which is the average usage for a three-person family.
IF YOU HAVE AN ELECTRIC AUXILIARY TANK SYSTEM:
You must understand or convert the cost of power into kilowatt-hours (kWh). In 2021, the average electricity rate in the United States was 10.42 cents per kilowatt-hour.
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The average power tariff in Hawaii is 30.55 cents per kilowatt-hour. The average electricity tariff in Louisiana is 7.01 cents per kilowatt-hour.
The average electricity tariff in Louisiana is 7.01 cents per kilowatt-hour. With a UEF of 1.0 and an electricity price of $0.1042/kWh, the annual water heating costs for an electric water heater are as follows: Annual Water Heating Cost = (365 days/year) 12.03 kWh/day (1.0) SEF ($0.1042) = $457.54/year
This example indicates that electricity is more expensive than natural gas, which is fairly common.
Cost Comparison and Return on Investment for a Solar Water Heating System
Now that we know what the cost of conventional heating is, we can estimate what it would be lowered to and deduct it to calculate the fuel savings associated with a solar water heater.
The power required to run pumps and controllers is also addressed in the SEF assessment. Annual Solar Energy Savings = Daily Hot Water Energy (therms per day)*(365 days per year)((1/EF)-(1/SEF))
The natural gas savings usage from a solar system with a SEF of 2.5, for example, would thus be
(0.4105 therms/day)*(365 days/year)((1/0.64)-(1/2.5)) =174 therms per year
Natural gas prices vary greatly depending on region and month. The average price in the United States in May 2021 was $1.776/therm, a considerable rise over previous years.
The average from 2011 to 2021 is around $1.50/therm, which we shall utilize in our scenario. The annual solar cost savings would be as follows:
- $261/year = (174 therms/year)*($1.50/therm)
The annual energy and cost savings for an electric water heater with UEF=1.0 and an electric price of $0.08/kWh are as follows:
- Annual Solar Energy Savings = (12.03 kWh/day) x 365 days per year ((1/1.0)-(1/2.5)) = 2634 kWh per year
And the corresponding annual solar cost savings would be:
$274.46/year = (2634 kWh/year)*($0.1042/kWh)
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